Adult Plum Curculios Research Articles

Response of Adult Plum Curculios (Coleoptera: Curculionidae) to Contrasting Shades in Field and Laboratory Experiments.

The responses of adult plum curculios, Conotrachelus nenuphar (Herbst), to visual stimuli were assessed in field and laboratory conditions to evaluate the hypothesis that adult captures should increase when traps visually contrast with a lighter horizon, such as the sky. Release-recapture field studies tested whether adult responses to traps were influenced by the trap's visual contrast with background on the horizon. Results at four sites showed that significantly more adults were captured in traps with woodlots behind them, refuting the hypothesis. Laboratory tests in environmental conditions of 315 lux or less observed the movement of adults between intervals. These showed that significantly more females and males relocated in areas marked with black. This effect occurred when adults were presented with black surfaces, stripes, or lines. The black shade used correlated with lower reflected lux (<110), and when in conditions of ≤ 10 lux, significant adult relocation on black was not observed. These results suggest that adults arrest in or move toward areas with low reflected lux. The laboratory and field results combined suggest that higher adult captures in traps correlated with the largest areas of low lux on the horizon. The results imply that trap placement should take reflected lux from all nearby objects into account and that even in small patterns on traps, variance in shade or reflected lux may permit manipulation of plum curculio movement.

Evaluating Electrophysiological and Behavioral Responses to Volatiles for Improvement of Odor-Baited Trap Tree Management ofConotrachelus nenuphar(Coleoptera: Curculionidae)

Plum curculio, Conotrachelus nenuphar (Herbst), one of the most important pests of apple in eastern and central North America, is usually managed in New England apple orchards by multiple full-block insecticide applications. Efforts to reduce insecticide inputs against plum curculio include using an "attract and kill" approach: odor-baited trap trees deployed in the perimeter row of apple orchards. The standard approach is based on baiting apple trees with two olfactory stimuli, the fruit volatile benzaldehyde and the aggregation pheromone of plum curculio, grandisoic acid. We attempted to improve attraction, aggregation, and retention of adult plum curculios within specific baited trap tree canopies within apple orchards using an additional host plant volatile found to be highly stimulating in electroantennogram studies, trans-2-hexenal. We also attempted to increase aggregation using increased release rates of grandisoic acid. We found that trans-2-hexenal did not provide increased aggregation when deployed as an additional attractant within trap trees or when conversely deployed as a "push" component or repellent in perimeter trees lateral to the baited trap tree. Although increasing the release rate of grandisoic acid 5× actually appeared to increase overall aggregation within trap trees, it was not significantly different than that obtained using the standard dose. Therefore, we believe that the standard olfactory stimuli are sufficient to provide aggregation within trap trees, but that other means should be used to manage them after their arrival.

Impact of insecticide and fungicide residue contact on plum curculio, Conotrachelus nenuphar (Herbst), mobility and mortality: implications for pest management

BACKGROUNDAn evaluation was made of the effects of seven neurotoxic insecticides (esfenvalerate, indoxacarb, clothianidin, thiacloprid, azinphosmethyl, phosmet and imidacloprid), one insect growth regulator (novaluron) and two fungicides (myclobutanin and mancozeb), with water as the control, on the horizontal mobility of plum curculios exposed to dried pesticide residues. Mobility was recorded over a 2 h period using ethological tracking software. Mortality was recorded immediately after horizontal mobility experiments and 24 h later.RESULTSEsfenvalerate had the greatest impact on mobility. Immediately after exposure to this compound, plum curculios moved significantly greater distances and for a significantly longer period of time compared with all other compounds. After 24 h, esfenvalerate also led to high mortality rates (>86.0%). Exposure to azinphosmethyl and phosmet also led to high rates of mortality, although the impact on mobility was less pronounced. Exposure to indoxacarb, thiacloprid, imidacloprid, novaluron, myclobutanin and mancozeb had no impact on mobility and resulted in little to no mortality. Clothianidin affected mobility after a 2 h exposure period, and high mortality (60%) was recorded after 24 h.CONCLUSIONSThe results indicate that, in the context of a treated orchard, plum curculios exposed to dried pesticide residues may be capable of foraging before succumbing to toxicant exposure, while exposure to pesticides such as esfenvalerate may rapidly incapacitate adult plum curculios.

Influence of Orchard Weed Management Practices on Soil Dwelling Stages of Plum Curculio,Conotrachelus nenuphar(Coleoptera: Curculionidae)

Plum curculio, Conotrachelus nenuphar Herbst (Coleoptera: Curculionidae), is a key pest of peaches in the southeastern United States. Part of its life cycle, specifically, the pre-pupal, pupal and pre-adult stages are spent in the soil. Experiments were conducted in 2 peach orchards to evaluate the effects of some common orchard weed management practices on the development of the soil dwelling life stages of plum curculio. Four common orchard weed management practices (treatments) were evaluated in plots (3 m × 3 m) located under peach tree canopies: centipede grass, Eremochloa ophiuroides (Munro) understory (soil covered with centipede grass); weed free understory (bare soil, weeds removed with herbicide sprays); weedy (natural weeds) understory; and pine bark understory (soil covered with pine bark). Fewer numbers of adult plum curculio emerged from the centipede grass understory plots compared with weed free, weedy or pine bark treated understories. Similar results were obtained in the greenhouse: fewer adults emerged from centipede grass than bare soil in spring 2009. Possible reasons for the lower emergence of plum curculio in centipede grass plots are proposed.

ORGANIC FRUIT PRODUCTION NEEDS AND PEST MANAGEMENT PRACTICES IN THE SOUTHEASTERN UNITED STATES

In 2001, only 14% of the certified organic acreage in the United States occurred in the 12 southeastern (SE) states. Eight of the 12 Land Grant Universities in the SE region had a total of 329 acres certified organic for use in research and extension. In 2004, client-based focus groups identified needs for organic fruit production in the SE: go-to personnel to increase interaction between the University and organic producers; more science-based research on soil, pest and nutrient management; information to be summarized in printed guides on organic production budgets and organic production practices; and local market development. Recently, we demonstrated that several science-based, ecologically low-risk conventional practices could be adapted for organic fruit production. Demonstration blocks in Arkansas showed that first and late season generations of codling moth (CM) and Oriental fruit moth (OFM) could be controlled with CM granulosis virus and Spinosad against CM and Spinosad and Bt against OFM when integrated with mating disruption against the mid-season generations of CM and OFM. The result was less than 1% fruit damage at harvest. Plum curculio adults disperse into the perimeter of fruit orchards in the spring. When plum curculio adults were attracted to perimeter apple trees baited with dispensers releasing volatiles of grandisoic acid (aggregation pheromone) and one or two kairomone compounds, benzaldehyde and plum essence, they caused significantly more fruit feeding damage in baited trees than adjacent unbaited trees. There is potential for using Japanese plum trees or bait trees in apples to focus plum curculio damage. A further advantage occurs with the application of a nematode soil drench to reduce plum curculio larva survival in soil under baited trees. Green June beetle adults feed on ripening fruit. Multiple yellow funnel traps baited with a lure of five-component volatile blend = TRE#8607 or 91% isopropanol were very attractive to green June beetles and may have potential for use in mass trapping this pest.

Field Evaluation of Traps and Lures for Monitoring Plum Curculio (Coleoptera: Curculionidae) in Alabama Peaches

The plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is a key pest of peaches, Prunus persica (L.) Batsch, in North America. We evaluated the effectiveness of two widely used trap types (pyramid versus Circle traps) and commercially available synthetic lures for monitoring the pest in two peach orchards in Alabama during 2008 and 2009. The lures evaluated alone or in combinations included benzaldehyde (BZ) (a component of fruit odor), plum essence (PE) (a mixture of fruit odor extracted from food grade plum), and grandisoic acid (GA) (a male-produced aggregation pheromone of plum curculio). In general, pyramid traps captured more plum curculio adults than Circle traps, particularly during the first generation. Trap performance was improved numerically by the addition of BZ, PE, or GA alone (single lures) and was significantly enhanced by the addition of the combined BZ + PE lure. In both first and second generations, the combined BZ + PE lure increased plum curculio captures (significant in some trials) over unbaited traps and traps baited with single lures by approximately 1.5-21-fold and had the highest response indices (RIs), which is indicative of high attractiveness. The combined BZ + GA lure and the three-component BZ + PE + GA lure also captured numerically more plum curculio adults than unbaited traps or traps baited with single lures but the differences were rarely significant. Analysis of ratios of interaction suggests the possibility of synergistic interactions between BZ and PE and between BZ and GA; however, additive effects were concluded due to high sample errors. These results are discussed in relation to the physicochemical properties of the lures and the potential of using baited monitoring traps to aid plum curculio management decisions in peach orchards.

Host-tree-related differences in trap captures and electroantennogram activity of Conotrachelus nenuphar (Coleoptera: Curculionidae)

AbstractThe plum curculio, Conotrachelus nenuphar (Herbst), is a serious pest of stone and pome fruits (Rosaceae) in eastern North America. We recorded captures of adult plum curculios in the field and measured electroantennogram (EAG) activity in the laboratory associated with cultivars of four hosts, ‘Formosa’ Japanese plum (Prunus salicina Lindl.), ‘Stanley’ European plum (P. domestica L.), ‘Empire’ apple (Malus domestica Borkh.), and ‘Loring’ peach (P. persica (L.) Batsch) (Rosaceae) to determine whether hosts that may be attractive to the plum curculio under field conditions also elicit positive EAG responses. Trap captures of adults on ‘Formosa’ plum were significantly greater than on any other host, and corresponding headspace extracts also produced strong EAG responses throughout the active season. ‘Stanley’ plum and ‘Loring’ peach, the other stone-fruit hosts included in the study, elicited strong EAG responses throughout the season, although trap captures associated with these hosts were generally not as high as for ‘Formosa’ plum. Throughout the season, trap captures of adults were significantly lower for ‘Empire’ apple than for ‘Formosa’ plum, and EAG responses were much lower than for all stone-fruit hosts. Our results indicate that volatiles from ‘Formosa’ plum likely contain uniquecompounds or are comprised of ratios of stimulating compounds that make it much more attractive to plum curculio in the field.

Impact of Trap Architecture, Adjacent Habitats, Abiotic Factors, and Host Plant Phenology on Captures of Plum Curculio (Coleoptera: Curculionidae) Adults

Pyramid traps, 2.44 m and 3.66 m in height, were compared with standard-sized pyramid traps, 1.22 m in height, to assess the impact of trap architecture on captures of adult plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), in two apple (Malus spp.) orchards and a blueberry (Vaccinium spp.) planting. The effects of adjacent habitat (organic orchard versus wooded areas), abiotic factors, and phenological stages of apple also were assessed to determine whether these variables influenced trap captures. Standard-sized pyramidal traps captured significantly more adults than larger trap variants. In the apple orchards, most adults (70-80%) were captured before petal fall with the exception of blocks adjacent to the organic orchard (25%). Significantly more adults were captured along the edge of an apple orchard (managed using an integrated pest management strategy) facing an organic apple orchard (76%) than along the edge facing wooded areas (24%). There was a significant positive correlation between daily trap captures and mean daily temperatures before petal fall in apple orchards.

Impact of Temperature on Plum Curculio (Coleoptera: Curculionidae) Responses to Odor-Baited Traps

In 2005, captures of overwintered adult plum curculios, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), in standard black masonite pyramid traps deployed in apple (Malus spp.) orchards from half-inch green until fruit reached 7 mm and baited with known attractants did not result in significant captures compared with unbaited traps as they had in 2003 and 2004. These baits included the synthetic aggregation pheromone, grandisoic acid (GA) alone, a six-component synthetic host plant volatile combination (6-Tree) identified from foliar and woody tissues of a Stanley plum tree in combination with GA (6-Tree+GA), and the synthetic fruit volatile benzaldehyde (BEN) in combination with GA (BEN+GA). In 2005, the average daily temperature was below 13 degrees C, much cooler than in 2003 and 2004. We hypothesized that plum curculio could not discriminate between baited and unbaited traps because of reduced release rates of odor-bait stimuli due to their temperature-driven release system. From data collected from 2003 to 2005, we found that plum curculio captures in traps baited with GA alone, 6-Tree+GA, and BEN+GA were significantly related to temperature. We created a predictive model to determine the level of activity, i.e., trap captures in baited traps compared with unbaited traps, we would expect to observe at a particular temperature for these same odor stimuli. Our models predicts that at temperatures between approximately 11 to 13 degrees C we would expect to see no difference between captures in baited and unbaited traps. For captures in odor-baited traps to reach twice those in unbaited traps, our model predicts that temperatures must reach 19.2 degrees C for GA alone, 18.5 degrees C for 6-Tree+GA, and 15.8 degrees C for BEN+GA.

Impact of Temperature on Plum Curculio (Coleoptera: Curculionidae) Responses to Odor-Baited Traps

In 2005, captures of overwintered adult plum curculios, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), in standard black masonite pyramid traps deployed in apple (Malus spp.) orchards from half-inch green until fruit reached 7 mm and baited with known attractants did not result in significant captures compared with unbaited traps as they had in 2003 and 2004. These baits included the synthetic aggregation pheromone, grandisoic acid (GA) alone, a six-component synthetic host plant volatile combination (6-Tree) identified from foliar and woody tissues of a Stanley plum tree in combination with GA (6-Tree+GA), and the synthetic fruit volatile benzaldehyde (BEN) in combination with GA (BEN+GA). In 2005, the average daily temperature was below 13°C, much cooler than in 2003 and 2004. We hypothesized that plum curculio could not discriminate between baited and unbaited traps because of reduced release rates of odor-bait stimuli due to their temperature-driven release system. From data collected from 2003 to 2005, we found that plum curculio captures in traps baited with GA alone, 6-Tree+GA, and BEN+GA were significantly related to temperature. We created a predictive model to determine the level of activity, i.e., trap captures in baited traps compared with unbaited traps, we would expect to observe at a particular temperature for these same odor stimuli. Our models predicts that at temperatures between ≈ 11 to 13°C we would expect to see no difference between captures in baited and unbaited traps. For captures in odor-baited traps to reach twice those in unbaited traps, our model predicts that temperatures must reach 19.2°C for GA alone, 18.5°C for 6-Tree+GA, and 15.8°C for BEN+GA.

Moisture Effects on Development and Survival of the Plum Curculio (Coleoptera: Curculionidae)

Laboratory-reared larvae of Conotrachelus nenuphar Herbst were exposed to three soil moisture treatments in pots containing a mix of soil and vermiculite, whereby pots were either watered daily (wet treatment) or watered to saturation when matric potential reached threshold values of −160 and −800 kPa for the intermediate and dry treatments, respectively. Adult emergence began at approximately the same time in the 3 treatments, but peak emergence (occurring ~1 month after the start of the experiment and within 2 wks of the beginning of emergence) was much more pronounced in the intermediate moisture treatment than in the wet and dry ones. In addition, cumulative emergence in the intermediate moisture treatment (corresponding to &amp;gt;40% of the initial number of larvae used in the experiment) was higher than in the wet (~30%) and dry (~20%) treatments. Approx. 25% of the adults that emerged from the dry treatment were underdeveloped and/or malformed. In a separate set of experiments, the effect of air humidity on survival of laboratory-reared plum curculio adults was investigated. Survival analysis revealed a significant (P&amp;lt; 0.0001) effect of vapor pressure deficit on adult longevity. As vapor pressure deficit decreased from ~2.8 to 0.009 kPa, median life expectancy increased from 1.1 to 9.0 d for insects without food supply and from 7.0 to 30.5 d for insects feeding on apples. Longevity correlated with cumulative water loss from the insects, which was lowest in a saturated atmosphere and greatest for insects exposed to a vapor pressure deficit of ~2.8 kPa. Cuticular permeability of C. nenuphar to water was calculated as 185.8 μg cm−2 kPa−1.

Host preference of the plum curculio

AbstractWe assessed host preference of adult plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), based on the total number of mark‐released and wild adults recovered and the total distance moved by mark‐released adults in an orchard whose layout was designed to specifically allow foraging plum curculios to choose among host tree species. Host trees included apple, Malus domestica Borkh.; pear, Pyrus communis (L.); peach, Prunus persica (L.) Batsch; apricot, Prunus armeniaca L.; tart cherry, Prunus cerasus L.; sweet cherry, Prunus avium (L.); European plum, Prunus domestica L.; and Japanese plum, Prunus salicina Lindl. (all Rosaceae). We released 2900 marked adults and recovered 17.7%. We used screen traps to provide a measure of the number of adults that arrived at and climbed up particular host trees and found that significantly greater numbers of marked adults and the greatest number of wild adults were recovered from screen traps attached to Japanese plum. We sampled host tree canopies by tapping limbs to provide a measure of the number of adults within a tree canopy at a particular moment. Again, significantly greater numbers of marked and wild adults were recovered from plum species, with no difference between Japanese and European plum cultivars for marked individuals, but with significantly greater numbers of wild individuals recovered from Japanese plum. The preference index (PI) for Japanese plum based on total distances moved by all marked adults recovered on Japanese plum divided by the total distance moved by marked adults recovered on other host trees indicated that Japanese plum was the most highly preferred host, followed by European plum, peach, sweet cherry, tart cherry, apricot, apple, and pear, respectively.

Use of Residue Profile Analysis to Identify Modes of Insecticide Activity Contributing to Control of Plum Curculio in Apples

Residue profile analysis techniques were developed, along with laboratory and field-based bioassays to describe the modes of insecticidal activity responsible for the control of the plum curculio, Conotrachelus nenuphar (Herbst), in apples (Malus spp.). Adult plum curculios were treated in laboratory topical bioassays to determine acute contact activity and lethal time for five insecticides. Azinphosmethyl had the highest levels of toxicity and shortest lethal time values, followed by the neonicotinoids thiacloprid, thiamethoxam, and imidacloprid, whereas indoxacarb had the highest LD50 and LT50 values for topical exposure. Field-based residual activity bioassays assessed adult mortality, and fruit and leaf injury from plum curculio exposed to 4 h, 7 d, and 14 d field-aged residues. All compounds caused significant levels of mortality to plum curculio when adults were exposed to fruit clusters 4 h post-application. Thiacloprid, thiamethoxam, and imidacloprid showed oviposition deterrence, antifeedant, and repellency effects in the 7- and/or 14 d residual bioassays and protected fruit in the absence of significant lethal activity. Indoxacarb maintained lethal activity throughout the study intervals, with the incidence of plum curculio feeding, suggesting that ingestion is an important mode of entry. For the neonicotinoids thiacloprid, thiamethoxam and imidacloprid plum curculio mortality was highly correlated with fruit and leaf surface residues. As surface residues declined, sublethal effects such as oviposition deterrence and antifeedant effect remained. The value of the plant–insect–chemistry triad model for describing the temporal dimensions of insecticidal modes of activity and understanding a compound’s critical performance characteristics is discussed.

Use of Residue Profile Analysis to Identify Modes of Insecticide Activity Contributing to Control of Plum Curculio in Apples

Residue profile analysis techniques were developed, along with laboratory and field-based bioassays to describe the modes of insecticidal activity responsible for the control of the plum curculio, Conotrachelus nenuphar (Herbst), in apples (Malus spp.). Adult plum curculios were treated in laboratory topical bioassays to determine acute contact activity and lethal time for five insecticides. Azinphosmethyl had the highest levels of toxicity and shortest lethal time values, followed by the neonicotinoids thiacloprid, thiamethoxam, and imidacloprid, whereas indoxacarb had the highest LD50 and LT50 values for topical exposure. Field-based residual activity bioassays assessed adult mortality, and fruit and leaf injury from plum curculio exposed to 4 h, 7 d, and 14 d field-aged residues. All compounds caused significant levels of mortality to plum curculio when adults were exposed to fruit clusters 4 h post-application. Thiacloprid, thiamethoxam, and imidacloprid showed oviposition deterrence, antifeedant, and repellency effects in the 7- and/or 14 d residual bioassays and protected fruit in the absence of significant lethal activity. Indoxacarb maintained lethal activity throughout the study intervals, with the incidence of plum curculio feeding, suggesting that ingestion is an important mode of entry. For the neonicotinoids thiacloprid, thiamethoxam and imidacloprid plum curculio mortality was highly correlated with fruit and leaf surface residues. As surface residues declined, sublethal effects such as oviposition deterrence and antifeedant effect remained. The value of the plant-insect-chemistry triad model for describing the temporal dimensions of insecticidal modes of activity and understanding a compound's critical performance characteristics is discussed.

Nonfruiting Host Tree Volatile Blends: Novel Attractants for the Plum Curculio (Coleoptera: Curculionidae)

Abstract We evaluated the attractiveness of novel synthetic host plant volatiles alone and in combination with the synthetic aggregation pheromone, grandisoic acid (GA), to overwintered adult plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) in association with black masonite pyramid traps deployed in an unsprayed apple orchard in 2003 and 2004. Synthetic host plant volatiles evaluated included (1) those identified from foliar and woody tissues of a nonfruiting Stanley plum tree (6-Tree) or the two major components (2-Tree); (2) those identified from Stanley plum fruit (7-Plum) or two components eliciting positive GC-EAD response from plum curculios (2-Plum); and (3) benzaldehyde formulated into rubber septa and replaced weekly [Ben(s)] or dispensed into polyethylene vials and replaced weekly [Ben(r)], not replaced [Ben(nr)], and formulated with 10% 1,2,4-trichlorobenzene and not replaced [Ben(TCB)]. In 2003, the greatest numbers of plum curculios were captured in traps baited wit...

HYPOXIA REDUCES REPRODUCTIVE SUSCEPTIBILITY OF PLUM CURCULIO (COLEOPTERA: CURCULIONIDAE) TO IONIZING RADIATION

Ionizing irradiation is used in Florida and Hawaii to disinfest several fruits and sweetpotatoes of fruit flies (Diptera: Tephritidae) or other insects (Hallman 2004a). Importation of fruit irradiated against 11 fruit fly species and the mango seed weevil, Cryptorhynchus mangiferae (F.) (Coleoptera: Curculionidae), has been approved (APHIS 2002). The treatment shows promise for widespread implementation, as it is safe, broadly efficacious, accepted by consumers, cost-effective, may be applied after packing, and widely tolerated by fresh agricultural commodities (Hallman 2002). A large body of research has determined minimum absorbed doses of ionizing radiation to prevent development or reproduction for many different species of arthropods . Some of this research has shown that hypoxia can reduce some of the detrimental effects of irradiation to insects used in sterile release programs. The effect of hypoxia on irradiation disinfestation treatment efficacy has not been studied until recently, although some agricultural commodities are stored under hypoxic conditions, a strategy that is increasing in application. Hallman (2004a) found that while no oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), fifth instars developed to the adult stage when irradiated at 200 Gy in ambient atmosphere, 5.3% of those irradiated in hypoxic atmospheres developed to the adult. Hypoxia caused a small increase in the ability of apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), third instars to emerge as adults after irradiation (Hallman 2004b). Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is native to the eastern Neartic and is a quarantine pest of stone and pome fruits exported from the United States and Canada. Hallman (2003) determined that a minimum absorbed dose of 92 Gy (the maximum recorded dose when 80 Gy was sought) prevented reproduction of adults, the most radiotolerant stage of the insect. The objective of this research was to determine the effect of hypoxia on reproduction of the plum curculio. Plum curculios originally collected near Gainesville, Florida, were obtained from a colony at the United States Department of Agriculture, Agricultural Research Service facility in Byron, Georgia. The insects were reared at about 25EC, 70% RH, 12: 12h (L: D), on immature apples that were picked when about 3 cm in diameter. Larvae emerging from the apples were placed on sterilized potting soil until adult emergence. A radiation source of 137Cs (Husman Model 521A, Isomedix, Inc., Whippany, NJ) that delivered a gamma ray dose rate of about 40 Gy min-' was used in this research. Routine dosimetry was done with radiochromic film (Gafchromic MD-55, ISP Technologies, Inc., Wayne, NJ) and read with a spectrophotometer at 510 nm (Milton Roy Spectronic 401, Ivyland, PA). Adult plum curculios were irradiated in ambient atmospheres and in atmospheres of mostly nitrogen. Cylinders (polyvinyl chloride, 37.5 cm inside length, 10 cm inside diameter) fitted on one end with a screw cap sealed with vacuum grease and on the other end with 2 brass, barbed-nipple compression hose fittings (25 mm long, 4-mm inside diameter) were constructed. Two-week-old plum curculio adults were placed inside the cylinder with a few immature apples, and the atmosphere was purged through the hose fittings with nitrogen at a pressure of about 3 kPa for 2 minutes 20, 16, and 2 h before irradiation with an absorbed dose of 40 Gy. After purging, the hose fittings were sealed with rubber septa and the cylinders held at about 24?C. About 1.5 h after irradiation, the cylinders were opened to return the insects to ambient atmosphere. There were 6 replicates of 300-600 each for adults irradiated in ambient or hypoxic atmospheres. Controls consisted of 6 replicates of 30-100 insects each in a cylinder under ambient atmosphere that were not irradiated. After irradiation, adults were maintained on immature apples at about 25?C, and mortality was determined every week. The apples were replaced every week and maintained at 25?C for development of any immatures inside. Larvae emerging from apples were collected every 1-3 days and placed on potting soil for pupation and adult emergence. After larvae were no longer emerging, the apples were opened and any remaining insects collected. Analyses of variance were done with Prism 4 (www.graphpad.com). The mortality rate for the irradiated plum curculios was greater than that for the control until 15 weeks after irradiation when the rate for the control accelerated (Fig. 1). There was no significant difference among the treatments for time to reach 95% mortality (overall mean = 27.4 + 2.6 weeks, F = 1.56, P = 0.26, df: 2,15). Reproduction under irradiation and hypoxia was increased by over 20-fold compared with irradiation in ambient atmosphere (Table 1). Reproduction was greater than the 34.4 Gy for 4th instars per female reported by Hallman (2003) for

Ecology and management of plum curculio, Conotrachelus nenuphar [Coleoptera :Curculionidae], in apple orchards

Plum curculio (Conotrachelus nenuphar) is a native pest of pome and stone fruit in eastern North America. It is a key pest of apple (Malus pumila) orchards in Quebec. In spring, adults disperse primarily from woodland overwintering sites to apple orchards. Before fruit set, the beetles are mainly nocturnal. As fruits become available for oviposition, adults extend their activity to the daytime. Full grown larvae found in dropped apples in June (June drop) enter the soil to pupate. The summer brood emerges in August, feeds on the remaining fruit throughout the fall and then disperses to suitable overwintering sites. Little is known of its community and host plant relationships, dispersal behavior, factors influencing its mode of locomotion, choice of food sources, overwintering sites, micro-habitat selection, orientation, and action threshold. Commercially available biocontrol agents are not effective, and convenient and reliable monitoring techniques for the timing of sprays have not been developed. However, recent field and insectary studies on the behavior and activity of plum curculio adults may allow us to improve the efficiency of control strategies. These findings are presented here, together with their implications for control of the plum curculio by modifying its habitat, and by better timing and location of sprays and other interventions. This paper also includes brief reviews of biological controls, insect growth regulators, and genetic controls for plum curculio.

Spatial and Temporal Within-Canopy Distribution of Egglaying by Plum Curculios (Coleoptera: Curculionidae) on Apples in Relation to Tree Size

In a 3-yr study, we determined the spatial and temporal distribution of egglaying by adult plum curculios, Conotrachelus nenuphar (Herbst), among fruit within the canopies of small, medium and large apple trees located in unsprayed sections of commercial orchards in Massachusetts. For large and medium trees, fruit from 6 different tree sectors, corresponding to 3 canopy levels (top, mid and bottom) and 2 branch zones (outer vs inner), were sampled on a ~weekly basis. For small trees, fruit was sampled also ~weekly from the 3 to 4 sectors into which the tree canopies were divided. For large trees, early in the season more fruit were damaged at the tree tops, with a tendency towards a relatively homogeneous distribution of damage (from top to bottom) at the end of the sampling period. As the season progressed, more fruit was damaged at outer than inner zones of branches of large trees. For medium trees, the distribution of fruit damage according to canopy level varied across years: it tended to be uniform early in the season but, as the season progressed, damage to fruit was greatest at bottom and mid levels (2000) or at the tree tops (2001 (2002). In general, the extent of damage to fruit was similar at inner and outer zones of branches of medium trees. For small trees, level of fruit damage was similar at each of the canopy sectors and for each of the sampling periods. In most cases, a homogeneous or heterogeneous distribution of fruit having plum curculio injury corresponded with a homogeneous or heterogeneous within-canopy distribution of fruit size.

Field evaluation of plant odor and pheromonal combinations for attracting plum curculios.

The attractiveness of different synthetic host odors and a synthetic aggregation pheromone (grandisoic acid [GA]) to overwintered adult plum curculios (PCs), Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), was examined using two types of traps (sticky panels and black pyramids) placed in border areas surrounding an unsprayed section of an apple orchard in Massachusetts. In 2001, we evaluated the response of PCs to three synthetic fruit volatiles (benzaldehyde [BEN], ethyl isovalerate [EIV], and limonene [LIM]) assessed alone and in combination with GA, as well as the response to GA alone and a no-odor (control) treatment. BEN was the only host volatile that synergized the response of PCs to GA for both trap types. For both trap types, GA was as attractive to PCs as a single component as when in combination with either EIV or LIM. In 2002, four release rates of BEN (0, 2.5, 10, and 40 mg/day) and two release rates of GA (1 and 2 mg/day) were evaluated for attractiveness to PCs using panel and pyramid traps. For panel traps, an increase in amount of GA released (from 1 to 2 mg/day) was associated with a 35% increase in captures. However, PC captures by pyramid traps were similar regardless of the amount of GA released. For panel traps, 10 and 40 mg/day of BEN were the most attractive release rates regardless of the amount of GA released. For pyramid traps baited with GA. PC captures were enhanced by the presence of BEN, regardless of release rate. In 2003, GA at 1 mg/day + BEN at 80 mg/day of release did not enhance PC captures by panel traps relative to lower release rates of BEN. Pyramid traps releasing GA at 1 mg/day performed best when baited with BEN at 10 mg/day of release; a release rate of 80 mg/day of BEN decreased the attractiveness of the binary combination of BEN + GA. Combined results suggest that BEN at 10 mg/day + GA at 1 mg/day of release constitutes an attractive lure that may improve the effectiveness of monitoring traps for PCs.

Ionizing Irradiation Quarantine Treatment Against Plum Curculio (Coleoptera: Curculionidae)

Plum curculio, Conotrachelus nenuphar (Herbst), is a quarantine pest of many temperate fruits, such as pomes, Malus spp.; stone fruits, Prunus spp.; and blueberries, Vaccinium spp.; in North America east of the Rocky Mountains and a small area in Utah. There are two strains, a northern univoltine one that undergoes obligate diapause as an adult and a southern multivoltine strain that usually has facultative diapause. Current quarantine treatments for shipment to areas that do not have the pest include methyl bromide fumigation and cold storage for several weeks. The cold storage treatment may not be effective against northern strain adults in diapause. The objective of this research was to develop an irradiation quarantine treatment against plum curculio. The estimated dose to kill southern strain plum curculio adults in one day is ≈4 kGy. Diapausing northern strain plum curculios were prevented from reproducing with 40 Gy. Reproduction of southern strain plum curculios was prevented with a target dose of 80 Gy, and the dose recommended as a quarantine treatment, that would prevent adults from reproducing, is 92 Gy, the maximum absorbed dose measured when a target dose of 80 Gy was sought. At that dose, oviposition may still occur for up to 1 wk and some of the eggs may hatch, but there is no development beyond the first instar. Hosts of the plum curculio would tolerate that dose well. Immature plum curculios were prevented from reproducing with lower doses.